Influence of microstructure on the properties of bronze-processed multifilamentary wire

Technical Report · Sun May 01 04:00:00 EDT 1983

DOI:https://doi.org/10.2172/5864175· OSTI ID:5864175

Wu, I W; Dietderich, D R; Hassenzahl, W V; Morris, Jr, J W

The A15 layer of a commercial Airco wire containing 2869 Nb filaments was analyzed as a function of heat treatment. Its microstructure is composed of three morphologically concentric shells. The central shell consists of fine equiaxed grains and has a nearly stoichiometric Sn concentration. High resolution electron microscopic analysis suggests that the fine grains are formed through the polygonization of dislocations. The homogeneous composition through the fine-grained layer is a probable consequence of the small grain size, which permits relatively rapid chemical redistributions through grain boundary diffusion. In contrast, the chemical gradient in the large-grained inner and outer sheels is steep. The microstructure is established by the reaction heat treatment, and determines the critical current. The best combination of grain size, composition, and volume of the fine-grained shell is obtained with an intermediate reaction temperature (700 to 730/sup 0/C); this temperature range also yields the best values of J/sub c/. Various two-step heat treatments were studied and compared to isothermal aging. The best microstructure and, hence, the best critical current characteristic was obtained by aging the specimen at 700/sup 0/C for 4 days followed by 730/sup 0/ for 2 days.

• Research Organization: Lawrence Berkeley Lab., CA (USA)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 5864175
• Report Number(s): LBL-16230; CONF-8305124-1; ON: DE83016999
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
360104 -- Metals & Alloys-- Physical Properties
656102 -- Solid State Physics-- Superconductivity-- Acoustic
Electronic
Magnetic
Optical
& Thermal Phenomena-- (-1987)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALLOYS
COHERENT SCATTERING
CRITICAL CURRENT
CRYSTAL STRUCTURE
CURRENT DENSITY
CURRENTS
DATA
DIFFRACTION
ELECTRIC CONDUCTIVITY
ELECTRIC CURRENTS
ELECTRICAL PROPERTIES
ELECTRON DIFFRACTION
ELECTRON MICROSCOPY
EXPERIMENTAL DATA
GRAIN SIZE
HEAT TREATMENTS
INFORMATION
MICROSCOPY
MICROSTRUCTURE
NIOBIUM ALLOYS
NUMERICAL DATA
PHYSICAL PROPERTIES
SCATTERING
SIZE
SUPERCONDUCTING WIRES
SUPERCONDUCTIVITY
THERMODYNAMIC PROPERTIES
TIN ALLOYS
TRANSITION TEMPERATURE
WIRES